The 644180-7: This is a 13-position MTA-100 header from TE Connectivity, but only 4 of those positions are loaded with pins. The remaining 9 cavities are empty — the plastic housing is there, the contacts aren't. If your circuit count is 4, this saves you buying a fully populated 13-position part and leaving 9 pins unused. The single-wall shroud guides the receptacle into alignment, and the friction lock holds it there — no secondary latch needed.
Through-hole solder tail and tin plating — board assembly fit
The contact length on the post side is 0.140" (3.56mm) — standard for a 1.6mm PCB with a solder wave. That leaves enough pin length to engage the IDC receptacle's full beam depth.